"Observative" Natural Recordings by Native Speakers
Observative refers to being observant or having the ability to notice and pay attention to details, often with a keen sense of perception and insight. An observative person is someone who is able to observe and understand situations, people, and events accurately and in depth, often without needing to be explicitly told or shown.
I'm afraid there is no such word as "observantine". It's possible that it's a typo or a made-up word. If you meant to type a different word, please let me know and I'll be happy to help you with its meaning.